326 THE DESERT SANDSTONE. 



regions, especially when their origin was unknown has naturally 

 suggested one immense formation. 



Fluviatile Conglomerates. — These consist of a coarse, slightly 

 reddish, excessively hard quartzite, with numerous fine blackish 

 lines of specular iron. They enclose many rounded waterworn 

 quartz pebbles of various colours, sizes, and shapes, but all smoothed 

 by fluviatile action. These pebbles are white for the most part, 

 and generally sparingly scattered through the strata ; but there 

 are sometimes thick beds of conglomerate with fragments of slate 

 and numerous veins of segregated quartz of small size. There are 

 two kinds of stratification, namely, large divisional lines from one 

 foot to six feet and more apart, and cross stratification or false 

 bedding. Two peculiarities of this formation will now be 

 mentioned : — 1. The curious dip of the beds. 2. Its broken and 

 fragmentary character. 



1. The formation dips away to the east along the existing 

 streams at an angle of about 30 degrees ; that is to say the large 

 partings of the beds seem to have this dip ; but in this matter I 

 much regret that I had not an opportunity of making more 

 extensive observations, because sometimes I was inclined to think 

 that the beds have been truly upheaved to a high angle independent 

 of the false bedding or cross stratification. In other instances 

 there was not the same evidence of tilting. 



Mount Douglas will afford an illustration of what I am 

 describing. It is a conspicuous hill lying to the eastward of the 

 telegraph line about 100 miles south of Port Darwin. It forms 

 the extreme end of ranges of meridional hills of a very broken 

 character, though not exceeding 500 feet in height. Mount 

 Douglas itself is a castellated hill, quite abrupt on its south- 

 western end, and showing in section about 400 or 500 feet of the 

 fluviatile conglomerates I am now describing. The strata dip 

 away from the river McKinlay at an angle of 30 degrees or more; 

 and though the general appearance would lead one to believe that 

 this dip is due to a tilting of the beds, a more careful examination 

 induces me to think that ^this angle may represent the direction 

 of the current wherein the conglomerates were formed. There is 

 nothing in the neighbourhood to correspond with this inclination 

 of the beds, which are certainly the newest and uppermost rocks 

 to be seen hereabouts. At the Margaret River I noticed the same 

 dip of a similar conglomerate with similar appearances to those 

 met with at Mount Douglas, though the direction of the dip was 

 different. At Kekwick's Springs, on the tableland beyond the 

 head of the Mary, an outcrop of the same kind of conglomerate 

 was observed with the same high inclination in the general dip of 

 the beds. This outcrop was very small and there was no detached 

 tableland near it. At the head of the Katherine River about 1 2 



